Solid-state image sensor, imaging device, and electronic device

ABSTRACT

The present technology relates to a solid-state image sensor, an imaging device, and an electronic device capable of switching FD conversion efficiency in all pixels of a solid-state image sensor. A photodiode performs photoelectric conversion on incident light. A floating diffusion (FD) stores charge obtained by the photodiode. FD2, which is a second FD to which the capacity of an additional capacitor MIM is added, adds the capacity to the FD. The additional capacitor MIM is constituted by a first electrode formed by a wiring layer and a second electrode formed by a metallic light blocking film provided on a surface of a substrate on which the photodiode is formed. Switching between the FD and FD+FD2 allows switching of the FD conversion efficiency. The present technology is applicable to a CMOS image sensor.

TECHNICAL FIELD

The present technology relates to a solid-state image sensor, an imagingdevice, and an electronic device, and more particularly to a solid-stateimage sensor, an imaging device, and an electronic device capable ofswitching FD conversion efficiency in all pixels.

BACKGROUND ART

A solid-state image sensor (image sensor) having a feature of switchingthe conversion efficiency of floating diffusion (FD) provided in eachpixel has been proposed (refer to Patent Document 1).

Since the FD conversion efficiency is define by a value proportional toan inverse of a parasitic capacitance of the FD, the switching ofconversion efficiency is achieved by switching of the parasiticcapacitance.

The technology according to Patent Document 1 is based on a typicalComplementary Metal Oxide Semiconductor (CMOS) image sensor and providesa gate for switching between a first FD having a first capacity and asecond FD having a second capacity larger than the first capacity. Formaking the conversion efficiency higher, the gate is turned off so thatthe parasitic capacitance to the first FD is minimized, whereas formaking the conversion efficiency lower, the gate is turned on to connectthe first FD and the second FD with each other so that the parasiticcapacitance is maximized.

Furthermore, the technology of Patent Document 1 proposes combining(ZAF) pixels for imaging plane phase difference detection to switch theFD conversion efficiency.

In an image sensor having imaging plane phase difference detection,(ZAF) pixels for imaging plane phase difference detection for autofocusare embedded in a normal pixel array. A ZAF pixel is provided with alight blocking wiring layer for blocking part of incident light ascompared to a normal pixel. The light blocking wiring layer has a largerarea than other normal wirings owing to the property of blocking light.

In the technology of Patent Document 1, the ZAF light blocking wiringlayer is used to form parasitic capacitance as the second capacity forswitching the FD conversion efficiency, and switching of the conversionefficiency is achieve by switching the use of the parasitic capacitance.

CITATION LIST Patent Document

Patent Document 1: Japanese Patent Application Laid-Open No. 2014-112580

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

For maximizing sensitivity in a normal pixel, optimization is performedby focusing a microlens provided on the pixel surface on the surface ofa photodiode. In contrast, in a ZAF pixel, optimization is performed byfocusing a microlens on the surface of the light blocking film owing tothe phase difference detection characteristics.

Note that, since the light blocking wiring layer for ZAF is provided ata position away from the photodiode surface, the optimum curvature ofthe microlens is different in a normal pixel and a ZAF pixel. Thus, ifit is attempted to optimise the microlenses in both pixels, microlenseshaving different curvatures need to be produced for different pixels,which increases the number of processes and results in high cost. Ifpriority is given to the number of processes (priority is given to lowercost) and microlenses having the same curvature are used for all thepixels, at least either of the sensitivity characteristic of normalpixels and the phase difference detection characteristic of a ZAF pixelwill be sacrificed.

Furthermore, since a light blocking wiring layer for ZAF is used to formthe parasitic capacitance to be switched to, a capacity equivalentthereto cannot be formed in normal pixels that do not have lightblocking wiring layers. Thus, the technology of Patent Document 1 canonly be applied to ZAF pixels, which are only part of a solid-stateimage sensor, and cannot be applied to normal pixels.

The present technology is achieved in view of the aforementionedcircumstances and, in particular, enables switching of FD conversionefficiency in all pixels.

Solutions to Problems

A solid-state image sensor according to one aspect of the presenttechnology is a front-surface illuminated solid-state image sensorincluding: a photoelectric converter configured to perform photoelectricconversion of incident light; a charge-to-voltage converter configuredto store charge obtained by the photoelectric conversion; a chargestorage configured to add a capacity to the charge-to-voltage converter;and an additional capacitor configured to add a capacity to the chargestorage, wherein the additional capacitor is constituted by a firstelectrode formed by a wiring layer in which wiring electricallyconnected to terminals of the voltage converter and the charge storage,and a second electrode formed by a metallic layer provided on a surfaceof a substrate on which the photoelectric converter is formed, thesurface of the substrate being on a side closer to a light source of thelight, the metallic layer being provided closer to the substrate thanthe wiring layer is and being opposed to the wiring layer.

The charge storage and the additional capacitor may be provided for eachpixel having the photoelectric converter, and when charge is stored inthe charge-to-voltage converter in a given pixel, the charge storageprovided in the given pixel may add a charge capacity including anadditional capacity stored by the additional capacitor to thecharge-to-voltage converter.

A switching unit configured to switch to either of a state in which thecharge-to-voltage converter and the charge storage are electricallyconnected with each other and a state in which the charge-to-voltageconverter and the charge storage are electrically disconnected from eachother may further be included.

The metallic layer may be a light blocking film made of metal.

The metallic layer may be a light blocking film made of tungsten.

The light blocking film may be formed for forming a pixel for imagingplane phase difference detection.

When a polysilicon layer is provided on the surface of the substrate onthe side of the light source of the light, the light blocking film maybe formed on the polysilicon on the substrate.

The light blocking film may be formed on a transfer gate constituted bythe polysilicon layer provided on the surface of the substrate on theside of the light source of the light.

The light blocking film may shield any of an upper portion, a lowerportion, a left portion and a right portion of the photoelectricconverter.

The wiring layer may foe closer to the second electrode than a wiringlayer of typical wiring is.

The solid-state image sensor is of a global shutter-type, thesolid-state image sensor may further include a storage unit configuredto store pixel signals of respective pixels required for the globalshutter type, and the light blocking film may shield the storage unit.

The first electrode may be provided at a position opposed to the lightblocking film on the storage unit.

An imaging device according to one aspect of the present technology isan imaging device including a front-surface illuminated solid-stateimage sensor, the imaging device including: a photoelectric converterconfigured to perform photoelectric conversion of incident light; acharge-to-voltage converter configured to store charge obtained by thephotoelectric conversion; a charge storage configured to add a capacityto the charge-to-voltage converter; and an additional capacitorconfigured to add a capacity to the charge storage, wherein theadditional capacitor is constituted by a first electrode formed by awiring layer in which wiring electrically connected to terminals of thevoltage converter and the charge storage, and a second electrode formedby a metallic layer provided on a surface of a substrate on which thephotoelectric converter is formed, the surface of the substrate being ona side closer to a light source of the light, the metallic layer beingprovided closer to the substrate than the wiring layer is and beingopposed to the wiring layer.

An electronic device according to one aspect of the present technologyis an electronic device including a front-surface illuminatedsolid-state image sensor, the electronic device including: aphotoelectric converter configured to perform photoelectric conversionof incident light; a charge-to-voltage converter configured to storecharge obtained by the photoelectric conversion; a charge storageconfigured to add a capacity to the charge-to-voltage converter; and anadditional capacitor configured to add a capacity to the charge storage,wherein the additional capacitor is constituted by a first electrodeformed by a wiring layer in which wiring electrically connected toterminals of the voltage converter and the charge storage, and a secondelectrode formed by a metallic layer provided on a surface of asubstrate on which the photoelectric converter is formed, the surface ofthe substrate being on a side closer to a light source of the light, themetallic layer being provided closer to the substrate than the wiringlayer is and being opposed to the wiring layer.

In one aspect of the present technology, a front-surface illuminatedsolid-state image sensor is included, photoelectric conversion isperformed on incident light by a photoelectric converter, chargeobtained by the photoelectric conversion is stored by acharge-to-voltage converter, a capacity is added to thecharge-to-voltage converter by a charge storage, a capacity is added tothe charge storage by an additional capacitor, and the additionalcapacitor is formed by a first electrode formed by a wiring layer inwhich wiring electrically connected to terminals of the voltageconverter and the charge storage is formed, and a second electrodeformed by a metallic layer provided on a surface of a substrate on whichthe photoelectric converter is formed, the surface of the substratebeing on a side closer to a light source of the light, the metalliclayer being provided closer to the substrate than the wiring layer isand being opposed to the wiring layer.

Effects of the Invention

According to one aspect of the present technology, the FD conversionefficiency can be switched in all the pixels of a solid-state imagesensor.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing an example configuration of a solid-stateimage sensor.

FIG. 2 is diagram for explaining an example configuration of each pixelon a substrate.

FIG. 3 is a diagram for explaining an example configuration of eachpixel on a pixel array in FIG. 1.

FIG. 4 is a diagram for explaining an example configuration of ametallic light blocking film formed on a substrate in FIG. 3.

FIG. 5 is a diagram for explaining a configuration of a FD wiring layerformed on a layer constituted by the light blocking film in FIG. 4.

FIG. 6 is a diagram for explaining cross sections of a laminate of thelayers of FIGS. 3 to 5.

FIG. 7 is a diagram for explaining a first modified example, which isanother example configuration of a metallic light blocking film formedon the substrate in FIG. 3.

FIG. 8 is a diagram for explaining a second modified example, which isan example configuration in which a FD wiring layer is formed in a layercloser to the substrate than the aforementioned FD wiring layer is.

FIG. 9 is a diagram for explaining an example configuration of eachpixel when the pixel array of FIG. 1 is of a global shutter type.

FIG. 10 is a diagram for explaining an example configuration of ametallic light blocking film formed on a substrate in FIG. 9.

FIG. 11 is a diagram for explaining a configuration of a FD wiring layerformed on a layer constituted by the light blocking film in FIG. 10.

FIG. 12 is a diagram for explaining cross sections of a laminate of thelayers of FIGS. 9 to 11.

FIG. 13 is a diagram for explaining another configuration of a FD wiringlayer formed on a layer constituted by the light blocking film in FIG.10.

FIG. 14 is a diagram for explaining cross sections in the case of FIG.13.

FIG. 15 is a diagram for explaining a configuration of an imaging deviceand an electronic device including a solid-state image sensor to whichthe present technology is applied.

FIG. 16 is a diagram showing examples of use of the solid-state imagesensor.

MODE FOR CARRYING OUT THE INVENTION

Embodiments to which the present technology is applied will be describedbelow with reference to the drawings.

First Embodiment <Example Configuration of Solid-State Image Sensor>

First, an example configuration of a solid-state image sensor to whichthe present technology is applied will be described. FIG. 1 is a diagramshowing an example configuration of a solid-state image sensor to whichthe present technology is applied according to an embodiment.

A solid-state image sensor 11 is a front-surface illuminated imagesensor constituted by a Complementary Metal Oxide Semiconductor (CMOS)image sensor or the like, and is configured to take an image byreceiving light from an object, performing photoelectric conversionthereon, and generating an image signal.

Note that a front-surface illuminated image sensor is an image sensorhaving a configuration in which a light receiving surface on which lightfrom an object is incident, that is, microlenses (on-chip lenses) forfocusing light and a wiring layer having wiring of transistors and thelike for driving respective pixels are provided on photodiodes thatreceive light from an object.

The solid-state image sensor 11 includes a pixel array unit 21, avertical drive unit 22, a column processing unit 23, a horizontal driveunit 24, a system control unit 25, pixel drive lines 26, vertical signallines 27, a signal processing unit 28, and a data storage unit 29.

In the solid-state image sensor 11, the pixel array unit 21 is formed ona semiconductor substrate (chip), which is not shown, and the verticaldrive unit 22 to the system control unit 25 are further integrated onthe semiconductor substrate.

The pixel array unit 21 is constituted by pixels having photoelectricconversion elements for generating and storing an amount of chargecorresponding to the amount of incident light from an object, where thepixels constituting the pixel array unit 21 are arrangedtwo-dimensionally in the horizontal direction (row direction) and thevertical direction (column direction) in FIG. 1.

For example, in the pixel array unit 21, a pixel drive line 26 is wiredalong the row direction for each pixel row constituted by pixelsarranged in the row direction, and a vertical signal line 27 is wiredalong the column direction for each pixel column constituted by pixelsarranged in the column direction.

The vertical drive unit 22 includes a shift register, an addressdecoder, and the like, and is configured to supply signals or the liketo the respective pixels via the pixel drive lines 26 to drive thepixels of the pixel array unit 21 all at the same time, in units of arow, or the like.

The column processing unit 23 reads signals from the pixels of eachpixel column of the pixel array unit 21 via the vertical signal lines27, and performs noise removal, correlated double sampling. Analog toDigital (A/D) conversion, and the like to generate a pixel signal.

The horizontal drive unit 24 includes a shift register, an addressdecoder, and the like, and is configured to sequentially select unitcircuits, which are associated with the pixel columns, of the processingunit 23. As a result of this selective scanning of the horizontal driveunit 24, pixel signals subjected to signal processing for each unitcircuit by the column processing unit 23 are sequentially output to thesignal processing unit 28.

The system control unit 25 includes a timing generator for generatingvarious timing signals, and is configured to perform drive control ofthe vertical drive unit 22, the column processing unit 23, and thehorizontal drive unit 24 on the basis of the timing signals generated bythe timing generator.

The signal processing unit 28 temporarily stores data into the datastorage unit 2S where necessary, performs signal processing such ascomputation on pixel signals supplied from the column processing unit23, and outputs an image signal constituted by the pixel signals.

<Pixel Circuit Configuration>

Next, a circuit configuration of each of the pixels of the pixel arrayunit 21 described above will be described. FIG. 2 is a circuit diagramshowing an example circuit configuration of one of the pixels providedin the pixel array unit 21.

In FIG. 2, a pixel of the pixel array unit 21 includes a photodiode 61,a transfer gate 62, a charge-to-voltage converter 63, a capacity switch64, a charge storage 65, a reset gate 66, an amplification transistor67, and a selection transistor 68.

The photodiode 61 is a photoelectric conversion element constituted by ap-n junction photodiode, for example, and is configured to receive lightfrom an object, generate an amount of charge corresponding to the amountof received light by photoelectric conversion, and store the generatedcharge.

The transfer gate 62 is provided between the photodiode 61 and thecharge-to-voltage converter 63, and configured to transfer the chargestored in the photodiode 61 to the charge-to-voltage converter 63according to a drive signal TRG applied to a gate electrode of thetransfer gate 62.

In FIG. 2, for example, the transfer gate 62, the capacity switch 64,the reset gate 66, and the selection transistor 68 are constituted byn-channel MOS transistors.

Drive signals TRG, FDG, RST, and SEL are supplied to gate electrodes ofthe transfer gate 62 to the selection transistor 68, respectively. Thesedrive signals are pulse signals that are in active states (ON states) athigh level and in inactive states (OFF states) at low level.

Thus, at the transfer gate 62, for example, when the drive signal TRGsupplied to the gate electrode of the transfer gate 62 is in the activestate and the transfer gate 62 is thus turned on, the charge stored inthe photodiode 61 is transferred to the charge-to-voltage converter 63.

The charge-to-voltage converter 63 is a floating diffusion region (FD)that converts the charge transferred from the photodiode 61 via thetransfer gate 62 into an electrical signal such as a voltage signal, andoutputs the resulting signal.

The charge-to-voltage converter 63 is connected with the reset gate 66,and also with a vertical signal line 27 via the amplification transistor67 and the selection transistor 68. Furthermore, the charge-to-voltageconverter 63 is also connected with the charge storage 65 via thecapacity switch 64. The charge storage 65 is a floating diffusion region(FD) that converts charge into an electrical signal such as a voltagesignal and further includes an additional capacitor MIM, which will bedescribed below. Note that the charge storage 65 is a floating diffusionregion (FD) but is represented by a circuit symbol of a capacitorbecause the charge storage 65 operates with the capacity including thatof the additional capacitor MIM, which will be described below.

The capacity switch 64 is turned on or off according to the drive signalFDG, so as to switch the connection between the charge-to-voltageconverter 63 and the charge storage 65 to either of an electricallyconnected state and an electrically disconnected state.

Specifically, the drive signal FDG is supplied to the gate electrode ofthe capacity switch 64, and when the drive signal FDG is turned on, thepotential right beneath the capacity switch 64 becomes deeper and thecharge-to-voltage converter 63 and the charge storage 65 areelectrically connected with each other.

Conversely, when the drive signal FDG is turned off, the potential rightbeneath the capacity switch 64 becomes shallower and thecharge-to-voltage converter 63 and the charge storage 65 areelectrically disconnected from each other.

Thus, a capacity can be added to the charge-to-voltage converter 63 andthe sensitivity of the pixel can be changed by turning the drive signalFDG on and off. Specifically, when the amount of change of the storedcharge is represented by ΔQ, and the amount of change of the voltage andthe capacity when the charge change amount is ΔQ are represented by ΔVand C, respectively, the relation of ΔV=ΔQ/C is satisfied.

With the capacity of the charge-to-voltage converter 63 being C_(FD) andthe capacity of the charge storage 65 being C_(FD2), the capacity C in aregion of a pixel from which a signal level is read is C_(FD)+C_(FD2)while the drive signal FDG is in the ON state. In contrast, when thedrive signal FDG is turned off, the capacity C changes to C_(FD), andthe voltage sensitivity with respect to the amount of charge change (theamount of voltage change: FD conversion efficiency) is thus increased.

As described above, in the solid-state image sensor 11, the sensitivityof a pixel is appropriately changed by turning the drive signal FDG onand off. For example, when the drive signal FDG is turned on, the chargestorage 65 is electrically connected with the charge-to-voltageconverter 63, and thus, part of the charge transferred, from thephotodiode 61 to the charge-to-voltage converter 63 is also stored inthe charge storage 65 in addition to the charge-to-voltage converter 63.

The reset gate 66 is an element for initializing (resetting) regionsfrom the charge-to-voltage converter 63 to the charge storage 65 asnecessary, and has a drain connected to a power supply of a power supplyvoltage VDD and a source connected to the charge-to-voltage converter63. The drive signal RST is applied as a reset signal to a gateelectrode of the reset gate 66.

When the drive signal RST is brought into the active state, the resetgate 66 becomes a conductive state, and the potentials of thecharge-to-voltage converter 63, etc. are reset to the power supplyvoltage VDD level. In other words, the charge-to-voltage converter 63,etc., are initialized.

The amplification transistor 67 has the gate electrode connected to thecharge-to-voltage converter 63 and a drain connected to the power supplyof the power supply voltage VDD, and functions as an input unit of asource follower circuit that reads charge obtained by photoelectricconversion at the photodiode 61. Specifically, the amplificationtransistor 67 has a source connected to the vertical signal line 27 viathe selection transistor 68, and thus constitutes a constant currentsource and the source follower circuit, which are connected to one endof the vertical signal line 27.

The selection transistor 68 is connected between the source of theamplification transistor 67 and the vertical signal line 27, and thedrive signal SEL is supplied as a selection signal to the gate electrodeof the selection transistor 68. When the drive signal SEL is broughtinto the active state, the selection transistor 68 becomes a conductivestate, and the pixel having the selection transistor 68 is brought intoa selected state. When the pixel is brought into the selected state, asignal output from the amplification transistor 67 is read by the columnprocessing unit 23 via the vertical signal line 27.

Furthermore, for the pixels, a plurality of drive lines are wired as thepixel drive lines 26 in FIG. 1 for each pixel row, for example. Thedrive signals TRG, FDG, RST, and SEL are thus supplied from the verticaldrive unit 22 into the pixels via the drive lines that are the pixeldrive lines 26.

<Pixel Physical Structure>

Next, a physical structure of the above-described pixel will bedescribed with reference to FIGS. 3 to 6. Note that the componentsdescribed with reference to FIG. 2 and components corresponding theretowill be designated by the same names and reference numerals, and thedescription thereof will not be repeated as appropriate.

FIG. 3 is a top view of a first layer of a pixel, in which an elementisolation layer, polysilicon, and contacts on the substrate are formed.Note that in FIGS. 3 to 5, the direction toward the drawing sheetsurface is the incident direction of the incident light, and that thephotodiode (PD) 61 in FIG. 3 is the light receiving surface.

In addition, FIG. 4 is a top view of a second layer, which is a layer onthe first layer (the second layer being a layer on the side of a lightsource with respect to the incident direction of the incident light) andwhere a light blocking film is formed. Hereinafter, the second layerwill also be referred to as a light blocking film layer.

Furthermore, FIG. 5 is a top view of a third layer, which is a layer onthe second layer and where wiring for connecting contacts is formed.Hereinafter, the third layer will also be referred to as a wiring layer.

Furthermore, FIG. 6 shows an A-A′ cross section a B-B′ cross section ofa pixel in a state where the first to third layers are laminated, inwhich the upper right part of FIG. 6 shows the A-A′ cross section of theupper left part of FIG. 6 in a case of a normal pixel.

Furthermore, the lower right part of FIG. 6 shows a side cross sectionof a pixel (ZAF pixel) for imaging plane phase difference detection,which is the B-B′ cross section of the lower left part of FIG. 6. Theside cross section in FIG. 6 is shown as a laminate of the first layershown in FIG. 3, which is the lowermost layer, the second layer shown inFIG. 4, and the third layer shown in FIG. 5 in this order upward in thedrawing.

Furthermore, in the cross sections of the upper right part and the lowerright part of FIG. 6, the direction from up to down in the drawing isthe incident direction of incident light. Black squares in FIGS. 3 to 5represent the positions of (well) contacts (electrodes), and circleswith vertical stripes in FIG. 6 represent points corresponding tocontacts where wires are connected.

Furthermore, the upper left part in each of FIGS. 3 to 6 shows a topview of the first layer of one pixel, and the right part of each ofFIGS. 3 to 6 shows a top view of four pixels of 2×2 pixels in thehorizontal direction and in the vertical direction. Furthermore, out ofthe four pixels 51-1 to 51-4 in the right part of each of FIGS. 3 to 6,the lower right pixel 51-4 is a ZAF pixel while the other pixels 51-1 to51-3 are normal pixels.

First, a physical configuration of the first layer of one pixel will beexplained with reference to the upper left part of FIG. 3. A pixel 51 inFIG. 3 is surrounded by an element isolation layer D, and provided withthe photodiode 61 in a substantially lower half area thereof.

The transfer gate (TRG) 62 is provided at an upper part of thephotodiode 61 in FIG. 3, and the transfer gate 62 is opened and closedfor transferring charge stored in the photodiode 61 to thecharge-to-voltage converter 63 constituted by the floating diffusionregion (floating diffusion (FD)).

The capacity switch 64 for controlling electrical connection between thecharge storage 65, which constitutes a second floating diffusion region(FD), and the charge-to-voltage converter 63 is provided on the left ofthe charge-to-voltage converter 63 in FIG. 3. Thus, the capacity switch64 is switched between on and off so that the charge storage 65 and thecharge-to-voltage converter 63 are electrically connected with anddisconnected from each other.

The reset gate 66 for discharging charge stored in the charge storage 65and the charge-to-voltage converter 63 is provided on the right of thecharge-to-voltage converter 63 in FIG. 3. Thus, the capacity switch 64is switched between on and off so that the charge storage 65 and thecharge-to-voltage converter 63 are electrically connected with anddisconnected from each other.

The amplification transistor 67 is provided on the right of the resetgate 66 in FIG. 3. As also shown in FIGS. 5 and 6, the amplificationtransistor 67 is electrically connected by wiring SI represented byvertical stripes, amplifies an electrical signal supplied from thecharge-to-voltage converter 63 and outputs the amplified signal to theselection transistor 68.

The selection transistor 68 is provided on the right of theamplification transistor 67 in FIG. 3. When the drive signal SEL isbrought into the active state, the selection transistor 68 becomes theconductive state, and a signal output from the amplification transistor67 is output via a contact SO connected to the vertical signal line 27.

The right part of FIG. 3 shows four pixels, which are the pixels 51-1 to51-4, of 2×2 pixels (horizontal direction×vertical direction), each ofwhich being the pixel 51 shown in the left part of FIG. 3. The pixels 51are arranged in the horizontal direction and the vertical direction inthis manner to form the pixel array unit 21.

Next, with reference to FIG. 4, the second layer, which functions as thelight blocking film layer formed by being stacked on the first layer onthe side of the light source of incident light with respect to thelight-receiving surface, will be explained.

A range represented by hatching in the right part of FIG. 4 is the lightblocking film 71. The light-blocking film 71 is made of tungsten, forexample. The light blocking film made of tungsten is a typical structurethat is used for reducing light incidence (smear) on a vertical transferpath in a Charge Coupled Device (CCD) image sensor. However, while thelight blocking film is used for smear reduction in CCDs, the lightblocking film 71 is used for achieving a pixel for imaging plane phasedifference detection.

Specifically, the lower right pixel 51-4 of the two vertical pixels×twohorizontal pixels in the right part of FIG. 4 is a pixel (ZAF pixel) forimaging plane phase difference detection. The other pixels 51-1 to 51-3are normal pixels having a layout in which the light blocking films 71are open above the photodiodes 61. In contrast, the pixel (ZAF pixel)for imaging plane phase difference detection has a layout in which partof the photodiode 61 is shielded by the light blocking film 71. In FIG.4, an example configuration in which the tops of the photodiodes 61 areshielded by the light blocking films 71 is shown.

In addition, since the light blocking film 71 forms the second layermade of a metallic layer formed between the first layer and the thirdlayer, the light blocking film 71 is not provided at points wherecontacts are formed, so as to prevent occurrence of electrical shortcircuits.

Next, a configuration of the third layer will be explained withreference to FIG. 5.

The third layer is a FD wiring layer in which FD wiring 91 representedby vertical stripes in FIG. 5 and electrodes 91 a for forming theadditional capacitors MIM for giving additional capacities to the chargestorages 65, which are the second FDs, are formed. The circles in thevertical stripes in FIG. 5, which are at positions corresponding to thecontacts represented by the black squares in FIGS. 3 and 4, representpoints where contacts are electrically connected. Furthermore, in thethird layer shown by vertical stripes, the electrodes 91 a having arectangular shape are paired with the light blocking films 71 atpositions, facing the electrodes 91 a, in the second layer providedunder the third layer, and form the additional capacitors MIM together.The capacities of the additional capacitors MIM are added to thecapacities of the charge storages 65, and the FD conversion efficiencyis thus lowered as described above.

Specifically, within ranges of A2-A′ and B2-B′ surrounded by dottedlines in the upper right part and the lower right part, respectively, ofFIG. 6, the electrode 91 a and the light blocking film 71 are opposed toeach other in the vertical direction in FIG. 6, and such a configurationforms the additional capacitor MIM. In addition, the electrode 91 a isconnected via a contact 65 a, which adds to the capacity of the chargestorage 65 of a floating diffusion layer (n+) in the first layer, andthe capacity switch 64 is turned on, which electrically connects withthe charge-to-voltage converter 63 that is a floating diffusion region.This allows the FD conversion efficiency to be lowered.

In contrast, within ranges A1-A2 and B1-B2 in the upper right part andthe lower right part, respectively, in FIG. 6, since the light blockingfilm 71 is not present and the additional capacitor MIM is not formed,the FD wiring 91 is connected with the charge-to-voltage converter 63,which is formed as the floating diffusion region (n+) in the firstlayer, via a contact 63 a. In this case, unless the capacity switch 64is turned on, the charge-to-voltage converter 63 has its own capacityonly, and thus the FD conversion efficiency will not be lowered.

Consequently, the charge-to-voltage converter 63 and the charge storage65 formed as described above are electrically connected with anddisconnected from each other by the capacity switch 64, and this enablesswitching of the FD conversion efficiency (sensitivity) of pixelsignals. Furthermore, with this configuration, since the FD conversionefficiency is switched according to whether or not the sum of thecapacities of the charge storage 65 and the additional capacitor MIM isadded to the capacity charge-to-voltage converter 63, this allows the FDconversion efficiency to be switched uniformly at all the pixels withoutdistinction between normal pixels and pixels for imaging plane phasedifference detection.

Furthermore, in a normal pixel, in order to maximize the sensitivity,the curvature of the microlens ML as shown in the upper right part andthe lower right-part of FIG. 6, for example, is adjusted so as to focuson the surface of the photodiode 61 (Si surface). In the case of a pixel(ZAF pixel) for imaging plane phase difference detection, focusing onthe position (height) of the light blocking film 71 maximizes thecharacteristic of the pixel for imaging plane phase differencedetection. Thus, if the light blocking film 71 and the surface (Sisurface) of the photodiode 61 differ greatly in height, microlenses MLwith different curvatures need to be used for normal pixels and forpixels for imaging plane phase difference detection so that thecurvatures so that the normal pixels and the pixels for imaging planephase difference detection respectively meet the above characteristics.It is therefore necessary to either increase the number of processes forprocessing or sacrifice any of the characteristics so as not to increasethe number of processes.

However, as shown in the upper right part and the lower right part ofFIG. 6, as a result of the light blocking film 71 being formed close tothe photodiode 61 (as a result of formation of the pixel for imagingplane phase difference detection using the light blocking film 71), thecharacteristics can be maximized with microlenses ML all having the samecurvature, which suppresses an increase in cost due to an increase inthe number of processes that would occur for processing of microlensesof different curvatures.

In addition, in view of light incident obliquely, it is advantageous toform the light blocking film 71 immediately on the photodiode 61 so asto form a pixel (ZAF pixel) for imaging plane phase differencedetection. Specifically, if the light blocking film 71 made of metal isformed in an upper layer at a height different from that of thephotodiode 61, light incident obliquely may not be blocked by the lightblocking film 71 but may pass through a gap between the light blockingfilm 71 and the Si surface and enter the photodiode 61. In contrast, asshown in the upper right part and the lower right part of FIG. 6, sincethe light blocking film 71 is formed immediately on the photodiode 61,oblique light will not enter the photodiode 61.

As described above, a metallic layer constituted by the light blockingfilm 71 is not provided in a layer immediately under the FD wiring 91,but the electrode 91 a is provided only above the light blocking film 71that forms the additional capacitor MIM for adding an additionalcapacity to the charge storage 65.

With this configuration, the capacity of the additional capacitor MIM isadded to the charge capacity of the charge-to-voltage converter 63,which allows the capacity of the charge storage 65 to be set to a largevalue, and the charge-to-voltage converter 63 and the charge storage 65are electrically connected with and disconnected from each other by thecapacity switch 64, which practically allows switching between floatingdiffusion regions having different diffusion capacitances.

Consequently, the capacity is increased and the FD conversion efficiencyis lowered by electrically connecting the charge-to-voltage converter 63and the charge storage 65 with each other by the capacity switch 64.Conversely, the capacity is decreased and the conversion efficiency isincreased by electrically disconnecting the charge-to-voltage converter63 and the charge storage 65 from each other by the capacity switch 64.As a result of switching the FD conversion efficiency in this manner,the sensitivity can be switched.

In a case of a configuration in which the light blocking film 71 underthe electrode 91 a in the third layer covers a polysilicon gate, thecapacity of the additional capacitor MIM can further be increased.Specifically, since the light blocking film 71 is formed in a shapefollowing the pattern of the underlying shape, the distance between thelight blocking film 71 and the electrode 91 a at a portion where thepolysilicon gate is present becomes smaller. As a result, as shown inthe upper right part and the lower right part of FIG. 6, for example, ina case where a gate electrode of the transfer gate 64 is provided, thesmaller distance between the light blocking film 71 and the electrode 91a increases the capacity of the additional capacitor MIM. Although thepolysilicon gate is given herein as an example, any structure risingtoward the upper layer from the surface of the substrate (Si) canproduce similar effects. For example, element, isolation with oxidefilms such as Locos may be used.

Furthermore, since the light, blocking films 71 are not only placed innormal pixels but also in pixels (ZAF pixels) for imaging plane phasedifference detection, the structures around the charge-to-voltageconverters 63 are common in normal pixels and pixels for imaging planephase difference detection, which makes the FD conversion efficienciesof the normal pixels and the pixels for imaging plane phase differencedetection basically the same as each other.

Thus, normal pixels and pixels (ZAF pixels) for imaging plane phasedifference detection have a common layout except for the portionsshielding the photodiodes 61 of the pixels (ZAF pixels) for imagingplane phase difference detection, which allows the conversion efficiencyto be the same in all the pixels. Consequently, such disadvantages thatmay be caused in subsequent processes due to the difference in the FDconversion efficiency between pixels are prevented.

Furthermore, if the light blocking films 71 are provided only in pixelsfor imaging plane phase difference detection, the light blocking film 71would be provided in small sizes because the number of is smaller thanthe number of normal pixels and the pixels for imaging plane phasedifference detection would thus be dotted in the pixel array unit 21.Since the light blocking films 71 would be electrically floating whenprovided in small sizes, the effect of generating the capacity forforming the charge storage 65 could not be produced. In order to preventthe light blocking films 71 from becoming electrically floating, thelight blocking films 71 need to be fixed to a power supply, GND, or thelike. If the wiring layout is changed therefor only in the pixels forimaging plane phase difference detection, there is a concern that thecapacities (conversion efficiencies) generated by the charge-to-voltageconverter 63 and the charge storage 65 are different from those ofnormal pixels, which is not preferable. For preventing the above, thelight blocking films 71 are also provided in normal pixels, so thatextraction to outside of the pixel array is possible only with the lightblocking films 71, and a certain potential is applied thereto at outsideof the pixel array 21 so that the light blocking films 71 will notbecome electrically floating.

First Modified Example

An example has been explained above in which the light blocking films 71are provided so as to shield the upper portions of the photodiodes 61 asshown in the upper left part of FIG. 7 in the formation of pixels forimaging plane phase difference detection. However, the light blockingfilms 71 may be provided in such a manner as to shield other portions ofthe photodiodes 61 as long as pixels for imaging plane phase differencedetection can be formed. Specifically, as shown in the upper right partof FIG. 7, the light blocking parts 71 may be provided so that lowerportions of the photodiodes 61 are shielded. Alternatively, as shown inthe lower left part and the lower right part of FIG. 7, the lightblocking parts 71 may be provided so that right portions andleft-portions of the respective photodiodes 61 are shielded.

Second Modified Example

While an example in which the gate electrode of the transfer gate 62 isprovided in the same metallic wiring layer as the FD wiring 91 has beendescribed above, a FD wiring layer 101 may be used as the wiring layerat the charge-to-voltage converter 63 and the charge storage 65 andcommon wiring 91 may be used instead of the FD wiring 91 described abovefor the gate electrode of the transfer gate 62, so that an electrode 101a forming an additional capacitor MIM is formed in a layer closer to thelight blocking film 71 as shown in FIG. 8, for example.

In FIG. 8, the left part shows a side cross section of a normal pixelcorresponding to the upper right part of FIG. 6, and the right partshows a side cross section of a pixel for imaging plane phase differencedetection corresponding to the lower right part of FIG. 6, each of whichshowing an example in which common wiring 91 is used instead of the FDwiring 91 described above and the FD wiring 101 is formed at a positioncloser to the light blocking film 71 than that of the above-described FDwiring 91.

With this configuration, since the electrode 101 a forming theadditional capacitor MIM is disposed at a position closer to the lightblocking film 71, the capacity of the additional capacitor MIM isincreased, which achieves a larger capacity together with the capacityof the charge storage 65 functioning as the second floating diffusionregion, which allows the FD conversion efficiency to be further lowered,and which allows switching between two FD conversion efficiencies with alarger difference therebetween.

Furthermore, like the FD wiring 101, only the FD wiring 101 may be madeto be wiring at a position close to the light blocking film 71, withoutchanging the distances between the other common wiring 91 and the lightblocking film 71. This allows the capacity between the common wiring 91other than the FD wiring 101 and the light blocking film 71 not to bechanged. As a result, it is possible to increase only the capacity ofthe additional capacitor MIM while preventing occurrence of failure suchas an operating delay of transistors caused by an increase in thecapacity between the common wiring 91 and the light blocking film 71.

Second Embodiment

While an example of a typical front-surface illuminated CMOS imagesensor has been described above, the image sensor may be a so-calledglobal shutter front-surface illuminated CMOS image sensor provided witha memory for each pixel and configured to simultaneously read pixelsignals in all the pixels.

FIGS. 9 to 12 are diagrams showing a first layer to a third layer of aglobal shutter front-surface illuminated CMOS image sensor and sidecross sections thereof corresponding to those of FIGS. 3 to 6,respectively. Note that, in FIGS. 9 to 12, the components having thesame functions as those in FIGS. 3 to 6 will be designated by the samenames and reference numerals, and the description thereof will not berepeated as appropriate.

Thus, FIGS. 9 to 12 differ from FIGS. 3 to 6 in that the pixels areshown as pixels 151 in FIGS. 9 to 12 while the pixels 51 are shown inunits of a pixel in FIGS. 3 to 6.

Furthermore, each pixel 151 is provided with a transfer gate (TRG2) 161for opening and closing a gate to a memory 171 (FIG. 12) thatsimultaneously stores a signal of charge accumulated by the photodiode(FD) 61 in units of a pixel, and an overflow gate (OFG) 162 forresetting the photodiode 61.

The transfer gate 161 is disposed to cover the memory 171. The transfergate 161 and the overflow gate 162 are driven by not-shown drive signalsTRG2 and OFG, respectively, which are pulse signals that are both inactive states (ON states) at high level and in inactive states (OFFstates) at low level.

In each pixel 151, as shown in pixels 151-1 to 151-4 in FIG. 10, a lightblocking film 71 is formed as a second layer that is an upper layer ofthe first layer including the photodiode 61. In this second layer aswell, the light blocking film 71 is not provided around contacts interms of preventing short circuits. Note that the light blocking film 71in the pixel 151 is made of tungsten, for example, and reduces lightincidence on the memory 171 (FIG. 12) (PLS=paraSitic light senSitivity:phenomenon similar to smear) in a global shutter CMOS image sensor.

Furthermore, as shown in FIG. 11, a third layer constituted by FD wiring91 is formed on the second layer constituted by the light blocking film71, and part of the third, layer forms an electrode 91 a.

In this configuration, within a range of C2-C′ enclosed by a dotted linein C-C′ cross section shown in FIG. 12, the electrode 91 a and the lightblocking film 71 are opposed to each other to form an additionalcapacitor MIM. In addition, the electrode 91 a is connected via acontact 65 a, and the capacity of the additional capacitor MIM is thusadded to the charge storage 65 constituted by the floating diffusionregion (n+ layer) that is the first layer.

In contrast, within a range C1-C2 shown in FIG. 12, the FD wiring 91 isconnected via a contact 63 a, and the charge-to-voltage converter 63functions as the floating diffusion region (n+ layer) that is the firstlayer. In the charge-to-voltage converter 63, however, since the lightblocking film 71 is not formed at the position opposed to the FD wiring91 and no additional capacitor MIM is formed, the charge storage 65 hasits own capacity only.

The charge-to-voltage converter 63 and the charge storage 65 formed asdescribed above are electrically connected with and disconnection fromeach other by the capacity switch 64, and this enables switching of theFD conversion efficiency (sensitivity) of pixel signals.

As a result, in the global shutter CMOS image sensor as well, theswitching of the FD conversion efficiency can be achieved in all thepixels.

Third Modified Example

While an example has been described above in which the light blockingfilm 71 and the electrode 91 a provided in the third layer are opposedto each other to form the additional capacitor MIM so that the capacityof the charge storage 65 is increased, the electrode 91 a may beprovided in another region as long as the electrode Sla is opposed tothe light blocking film 71, and an electrode 91 b may be formed insteadof the electrode 91 a as shown in FIG. 13, for example.

Specifically, in a pixel 151 of the global shutter CMOS image sensor,since the transfer gate 161, which is the polysilicon gate (TRG2) on thememory 171 occupying a relatively large area, is present on photodiode61, the electrode 91 b is formed as a layer thereon.

In this configuration, as shown in a range of D2-D′ enclosed by a dottedline in D-D′ cross section shown in FIG. 14, the electrode 91 b and thelight blocking film 71 are opposed to each other to form an additionalcapacitor MIM. In addition, the electrode 91 b is connected via acontact 65 a, and the capacity is thus added to the capacity of thecharge storage 65 constituted by the floating diffusion region (n+layer) that is the first layer.

In contrast, within a range D1-D2 shown in FIG. 14, the FD wiring 91 isconnected via a contact 63 a, and the charge-to-voltage converter 63 ofthe first layer functions as the floating diffusion region (n+ layer).In the charge-to-voltage converter 63, however, since the light blockingfilm 71 is not formed at the position opposed to the FD wiring 91, theadditional capacitor MIM is not formed, and since the capacity in thecase where the charge storage 65 is not connected is not added, thecharge-to-voltage converter 63 has its own capacity only.

Furthermore, as shown in FIG. 14, when the electrode 91 b is provided onthe transfer gate 171, the distance between the electrode 91 b and thelight blocking film 71 is closer than that, between the electrode 91 aand the light blocking film 71 shown in FIG. 12, the additional capacityof the additional capacitor MIM is also increased. Consequently, thecharge-to-voltage converter 63 and the charge storage 65 formed asdescribed above are electrically connected with and disconnected fromeach other by the capacity switch 64, and this enables switching of theFD conversion efficiency (sensitivity) of two types of pixel signalsthat vary largely.

As a result, in the global shutter CMOS image sensor in which theelectrode 91 b is formed in this manner, the switching of the FDconversion efficiency can also be achieved in all the pixels.

<Application to Electronic Device>

The above-described solid-state image sensor is applicable to variouselectronic devices including imaging devices such as digital stillcameras and digital video cameras, cellular phones having imagingfunctions, and other devices having imaging functions, for example.

FIG. 15 is a block diagram showing an example configuration of animaging device that is an electronic device to which the presenttechnology is applied.

An imaging device 201 shown in FIG. 15 includes an optical system 202, ashutter 203, a solid-state image sensor 204, a drive circuit 205, asignal processing circuit 206, a monitor 207, and a memory 208, and iscapable of taking still images and video.

The optical system 202 includes one or more lenses, and is configure toguide light (incident light) from an object to the solid-state imagesensor 204, and focus the light onto a light receiving surface of thesolid-state image sensor 204.

The shutter 203 is disposed between the optical system 202 and thesolid-state image sensor 204, and controls the light irradiation periodand the light blocking period of light to the solid-state image sensor204 under the control of the drive circuit 205.

The solid-state image sensor 204 is constituted by the above-describedsolid-state image sensor 11 or by a package including the solid-stateimage sensor 11. The solid-state image sensor 204 accumulates signalcharge for a certain period according to light focused on the lightreceiving surface via the optical system 202 and the shutter 203. Thesignal charge accumulated in the solid-state image sensor 204 istransferred according to a drive signal (timing signal) supplied fromthe drive circuit 205.

The drive circuit 205 outputs drive signals for controlling the transferoperation of the solid-state image sensor 204 and the shutting operationof the shutter 203 to drive the solid-state image sensor 204 and theshutter 203.

The signal processing circuit 206 performs various signal processing onthe signal charge output from the solid-state image sensor 204. An image(image data) obtained through the signal processing by the signalprocessing circuit 206 is supplied to the monitor 207 for display orsupplied to the memory 208 for storage (recording).

In the imaging device 201 having such a configuration as well, theswitching of the FD conversion efficiency can be achieved in all thepixels by applying the solid-state image sensor 1 instead of theaforementioned solid-state image sensor 204.

<Examples of Use of Solid-State Image Sensor>

FIG. 16 is a diagram showing examples of use of the above-describedsolid-state image sensor 11.

The above-described solid-state image sensor 11 can be used in a varietyof cases as follows where light such as visible light, infrared light,ultraviolet light, and X-ray is sensed as follows, for example:

-   -   devices configured to take images for appreciation use, such as        digital cameras and portable devices with camera functions,    -   devices for transportation use, such as vehicle-mounted sensors        for imaging the front, the back, the surrounding, the inside, or        the like of an automobile for safe driving such as automatic        stop, for recognition of a driver's condition, and the like,        surveillance cameras for monitoring running vehicles and roads,        and ranging sensors for measuring distances between vehicles,        etc.,    -   devices for home electronics use, such as television sets,        refrigerators, and air conditioners for imaging a gesture of a        user and operating a device according to the gesture,    -   devices for medical care use and health care use, such as        endoscopes and devices for receiving infrared light for        angiography,    -   devices for security use, such as surveillance cameras for crime        prevention and cameras for personal authentication,    -   devices for beauty care use, such as skin measurement devices        configured to image a skin and microscopes for imaging a scalp,    -   devices for sport use, such as action cameras and wearable        cameras for sports, and    -   devices for agricultural use such as cameras for monitoring        conditions of fields and crops.

The present technology can also have the following configurations.

(1) A front-surface illuminated solid-state image sensor including: aphotoelectric converter configured to perform photoelectric conversionof incident light; a charge-to-voltage converter configured to storecharge obtained by the photoelectric conversion; a charge storageconfigured to add a capacity to the charge-to-voltage converter; and anadditional capacitor configured to add a capacity to the charge storage,wherein the additional capacitor is constituted by a first electrodeformed by a wiring layer in which wiring electrically connected toterminals of the voltage converter and the charge storage, and a secondelectrode formed by a metallic layer provided on a surface of asubstrate on which the photoelectric converter is formed, the surface ofthe substrate being on a side closer to a light source of the light, themetallic layer being provided closer to the substrate than the wiringlayer is and being opposed to the wiring layer.

(2) The solid-state image sensor of (1), wherein the charge storage andthe additional capacitor are provided for each pixel having thephotoelectric converter, and when charge is stored in thecharge-to-voltage converter in a given pixel, the charge storageprovided in the given pixel adds a charge capacity including anadditional capacity stored by the additional capacitor to thecharge-to-voltage converter.

(3) The solid-state image sensor of (2), further including a switchingunit configured to switch to either of a state in which thecharge-to-voltage converter and the charge storage are electricallyconnected with each other and a state in which the charge-to-voltageconverter and the charge storage are electrically disconnected from eachother.

(4) The solid-state image sensor of (1), wherein the metallic layer is alight blocking film made of metal.

(5) The solid-state image sensor of (4), wherein the metallic layer is alight blocking film made of tungsten.

(6) The solid-state image sensor of (4), wherein

the light blocking film is formed for forming a pixel for imaging planephase difference detection.

(7) The solid-state image sensor of (4), wherein when a polysiliconlayer is provided on the surface of the substrate on the side of thelight source of the light, the light blocking film is formed on thepolysilicon on the substrate.

(8) The solid-state image sensor of (7), wherein the light blocking filmis formed on a transfer gate constituted by the polysilicon layerprovided on the surface of the substrate on the side of the light sourceof the light.

(9) The solid-state image sensor of (4), wherein the light blocking filmshields any of an upper portion, a lower portion, a left portion and aright portion of the photoelectric converter.

(10) The solid-state image sensor of (4), wherein the wiring layer iscloser to the second electrode than a wiring layer of typical wiring is.

(11) The solid-state image sensor of (4), wherein the solid-state imagesensor is of a global shutter type. the solid-state image sensor furtherincluding a storage unit configured to store pixel signals of respectivepixels required for the global shutter type, wherein the light blockingfilm shields the storage unit.

(12) The solid-state image sensor of (11), wherein the first electrodeis provided at a position opposed to the light blocking film on thestorage unit.

(13) An imaging device including a front-surface illuminated solid-stateimage sensor, the imaging device including: a photoelectric converterconfigured to perform photoelectric conversion of incident light; acharge-to-voltage converter configured to store charge obtained by thephotoelectric conversion; a charge storage configured to add a capacityto the charge-to-voltage converter; and an additional capacitorconfigured to add a capacity to the charge storage, wherein theadditional capacitor is constituted by a first electrode formed by awiring layer in which wiring electrically connected to terminals of thevoltage converter and the charge storage is formed, and a secondelectrode formed by a metallic layer provided on a surface of asubstrate on which the photoelectric converter is formed, the surface ofthe substrate being on a side closer to a light source of the light, themetallic layer being provided closer to the substrate than the wiringlayer is and being opposed to the wiring layer.

(14) An electronic device including a front-surface illuminatedsolid-state image sensor, the electronic device including: aphotoelectric converter configured to perform photoelectric conversionof incident light; a charge-to-voltage converter configured to storecharge obtained by the photoelectric conversion; a charge storageconfigured to add a capacity to the charge-to-voltage converter; and anadditional capacitor configured to add a capacity to the charge storage,wherein the additional capacitor is constituted by a first electrodeformed by a wiring layer in which wiring electrically connected toterminals of the voltage converter and the charge storage is formed, anda second electrode formed by a metallic layer provided on a surface of asubstrate on which the photoelectric converter is formed, the surface ofthe substrate being on a side closer to a light source of the light, themetallic layer being provided closer to the substrate than the wiringlayer is and being opposed to the wiring layer.

REFERENCE SIGNS LIST

11 Solid-state image sensor

21 Pixel array unit

51 Pixel

61 Photodiode

62 Transfer gate

63 Charge-to-voltage converter

64 Capacity switch

65 Charge storage

66 Reset gate

67 Amplification transistor

68 Selection transistor

71 Light blocking film

91 FD wiring

91 a Electrode

151 Pixel

161 Transfer gate

162 Overflow gate

What is claimed is: 1-14. (canceled)
 15. An image sensor comprising: aphotoelectric converter configured to perform photoelectric conversionof incident light; a charge-to-voltage converter configured to storecharge obtained by the photoelectric conversion; a charge storageconfigured to store charge transferred from the charge-to-voltageconverter; a switch electrically connected to the charge-to-voltageconverter and the charge storage; a wiring layer including a wiringelectrically connected to a terminal of the charge-to-voltage converterand a terminal of the charge storage; and a metallic layer disposedbetween the photoelectric converter and the wiring layer, wherein thecharge transferred from the charge-to-voltage converter is configured tobe stored in at least one of the wiring layer or the metallic layer. 16.The image sensor according to claim 15, wherein the charge storage isprovided for each pixel having the photoelectric converter, and whencharge is stored in the charge-to-voltage converter in a given pixel,the charge storage provided in the given pixel adds a charge capacity tothe charge-to-voltage converter, the added charge capacity including anadditional capacity stored by the at least one of the wiring layer orthe metallic layer.
 17. The image sensor according to claim 16, whereinthe switch is configured to switch to either of a state in which thecharge-to-voltage converter and the charge storage are electricallyconnected with each other and a state in which the charge-to-voltageconverter and the charge storage are electrically disconnected from eachother.
 18. The image sensor according to claim 15, wherein the metalliclayer is a light blocking film made of metal.
 19. The image sensoraccording to claim 18, wherein the metallic layer is a light blockingfilm made of tungsten.
 20. The image sensor according to claim 18,wherein the light blocking film is formed for phase differencedetection.
 21. The image sensor according to claim 18, wherein apolysilicon layer is provided on a surface of the substrate that is alight incident side, and the light blocking film is formed on thepolysilicon layer.
 22. The image sensor according to claim 21, whereinthe light blocking film is formed on a transfer gate that includes thepolysilicon layer provided on the surface of the substrate.
 23. Theimage sensor according to claim 18, wherein the light blocking filmshields one or more of an upper portion, a lower portion, a leftportion, and a right portion of the photoelectric converter.
 24. Theimage sensor according to claim 18, wherein, in a cross-sectional view,the light blocking film is closer to a control gate of the switch thanthe wiring.
 25. The image sensor according to claim 18, wherein theimage sensor comprises a global shutter type image sensor.
 26. The imagesensor according to claim 25, wherein the wiring layer is provided at aposition opposed to the light blocking film on a storage unit of theglobal shutter type image sensor.
 27. An electronic device comprising:an image sensor comprising: a photoelectric converter configured toperform photoelectric conversion of incident light; a charge-to-voltageconverter configured to store charge obtained by the photoelectricconversion; a charge storage configured to store charge transferred fromthe charge-to-voltage converter; a switch electrically connected to thecharge-to-voltage converter and the charge storage; a wiring layerincluding a wiring electrically connected to a terminal of thecharge-to-voltage converter and a terminal of the charge storage; and ametallic layer disposed between the photoelectric converter and thewiring layer, wherein the charge transferred from the charge-to-voltageconverter is configured to be stored in at least one of the wiring layeror the metallic layer.